1. Field of the Invention
The present invention relates to a procedure for determining the parameters of an electric drive that controls a synchronous elevator motor having permanent magnets.
2. Description of Related Art
Several methods and calculation programs have been developed to allow the adjustments of a converter used in elevator control to be made at the factory. Generally, the converter settings are calculated based on the motor and elevator data specified in a customer's order. Such calculations may be done relatively long before the elevator is actually delivered and installed in the shaft. Problems exist, however, due to the inaccuracy and divergence of both elevator data and motor data. The parameters describing the motor are usually given as typical values. These so-called name plate values may differ from the actual properties of the motor by several percentage units. When the frequency converter has been adjusted based on typical values, both the frequency converter and the elevator need additional adjustment at the site of installation. Adjustments carried out at the site of installation increase the installation time, thus increasing the total manufacturing and installation costs of the elevator.
Recently, a new type of synchronous motor with permanent magnets, described in international patent application WO 95/00432, has been developed for use in elevator drives. Although the use of this new motor type as an elevator component brings considerable advantages, as a consequence of the large diameter and discoid shape of its rotor/stator, certain manufacturing tolerances must have larger values. This in turn leads to a larger range of variation in the performance characteristics of the manufactured motors than in the case of conventional asynchronous motors. As this new type of elevator motor generally forms an integral part of the hoisting machinery of the elevator, the installation assembly containing the motor is relatively heavy, so it is difficult to handle, move or mount on a test bench. This makes it still more difficult to adjust the frequency converters in factory.
An object of the present invention is to eliminate the drawbacks mentioned above. A specific object of the invention is to provide a new type of method by which the parameters for the electric drive of previously-installed elevator can be determined and set as simply, quickly and economically as possible.